Re: [kvm-unit-tests PATCH v3 2/3] s390x/spec_ex: Add test introducing odd address into PSW

Janosch Frank
2023-03-17T09:27:05Z

On 3/15/23 16:54, Nina Schoetterl-Glausch wrote:
> Instructions on s390 must be halfword aligned.
> Introducing an odd instruction address into the PSW leads to a
> specification exception when attempting to execute the instruction at
> the odd address.
> Add a test for this.
>
> Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>

Acked-by: Janosch Frank <frankja@linux.ibm.com>

Some nits below.

> ---
> s390x/spec_ex.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/s390x/spec_ex.c b/s390x/spec_ex.c
> index 2adc5996..83b8c58e 100644
> --- a/s390x/spec_ex.c
> +++ b/s390x/spec_ex.c
> @@ -88,12 +88,23 @@ static void expect_invalid_psw(struct psw psw)
> invalid_psw_expected = true;
> }
>
> +static void clear_invalid_psw(void)
> +{
> + expected_psw = PSW(0, 0);
> + invalid_psw_expected = false;
> +}
> +
> static int check_invalid_psw(void)
> {
> /* Since the fixup sets this to false we check for false here. */
> if (!invalid_psw_expected) {
> + /*
> + * Early exception recognition: pgm_int_id == 0.
> + * Late exception recognition: psw address has been
> + * incremented by pgm_int_id (unpredictable value)
> + */
> if (expected_psw.mask == invalid_psw.mask &&
> - expected_psw.addr == invalid_psw.addr)
> + expected_psw.addr == invalid_psw.addr - lowcore.pgm_int_id)
> return 0;
> report_fail("Wrong invalid PSW");
> } else {
> @@ -112,6 +123,42 @@ static int psw_bit_12_is_1(void)
> return check_invalid_psw();
> }
>
> +extern char misaligned_code[];
> +asm ( ".balign 2\n"

Is the double space intended?
Looking at the file itself some asm blocks have no space before the "("
and some have one.

> +" . = . + 1\n"
> +"misaligned_code:\n"
> +" larl %r0,0\n"
> +" br %r1\n"
> +);

Any reason this is not indented?

> +
> +static int psw_odd_address(void)
> +{
> + struct psw odd = PSW_WITH_CUR_MASK((uint64_t)&misaligned_code);
> + uint64_t executed_addr;
> +
> + expect_invalid_psw(odd);
> + fixup_psw.mask = extract_psw_mask();
> + asm volatile ( "xr %%r0,%%r0\n"

While it will likely never make a difference I'd still use xgr here
instead of xr.

> + " larl %%r1,0f\n"
> + " stg %%r1,%[fixup_addr]\n"
> + " lpswe %[odd_psw]\n"
> + "0: lr %[executed_addr],%%r0\n"
> + : [fixup_addr] "=&T" (fixup_psw.addr),
> + [executed_addr] "=d" (executed_addr)
> + : [odd_psw] "Q" (odd)
> + : "cc", "%r0", "%r1"
> + );
> +
> + if (!executed_addr) {
> + return check_invalid_psw();
> + } else {
> + assert(executed_addr == odd.addr);
> + clear_invalid_psw();
> + report_fail("did not execute unaligned instructions");
> + return 1;
> + }
> +}
> +
> /* A short PSW needs to have bit 12 set to be valid. */
> static int short_psw_bit_12_is_0(void)
> {
> @@ -170,6 +217,7 @@ struct spec_ex_trigger {
> static const struct spec_ex_trigger spec_ex_triggers[] = {
> { "psw_bit_12_is_1", &psw_bit_12_is_1, false, &fixup_invalid_psw },
> { "short_psw_bit_12_is_0", &short_psw_bit_12_is_0, false, &fixup_invalid_psw },
> + { "psw_odd_address", &psw_odd_address, false, &fixup_invalid_psw },
> { "bad_alignment", &bad_alignment, true, NULL },
> { "not_even", &not_even, true, NULL },
> { NULL, NULL, false, NULL },